Overheating issues after replacing radiator, 1994 ST Hatcback, 7A-FE Options

[Noahwhite2014]

Yup, need some help, not sure whats wrong now. It will be long, but I'm trying to include every detail possible for the best possible help

So one day i was driving home, and my AC went warm. I was confused as it hadn't done that before. So i began to pay attention to my gauges very closely, everything was normal, temp gauge was just a hair before the middle. About 5 minutes later, when i was near home, still paying attention to my gauges, i heard a felt a pretty loud pop. Didn't know where it was from, and I didnt think it was my car as in my neighborhood we usually have construction going on, so i figured it was someone who just dropped something heavy nearby. And then about 100 feet further down i smelt coolant, took a look at my gauges, still normal, no overheating. And then pulled into my driveway about 200 feet after that. I popped the hood and steam started coming out from the sides of my hood. As i opened the hood i saw brownish splash marks everywhere and a Crack in my radiator about 10" in length with a gap between the crack of about 1mm.

Well i figured, 21 year old radiator made of plastic. Had to crack sometime, and it just happened to be while it was pressurized and i was driving. So i ordered a new radiator (Spectra premium radiator). I already had hoses (gates hk23rb kit) as i had planned to replace the old hoses which were beginning to show excessive wear. I was also planning to flush the cooling system when replacing the hoses so i let the fairly dirty coolant go... When i drained the coolant after the radiator had cracked, it was very brown and murky and had quite a substantial amount of rust in it. Drained everything, turned the heater to completely hot, put the output to feet and put the blower fan on max. Flushed with water till it was clear (couldn't get it perfectly clear even after 10 minutes AFTER it had gotten mostly clear).

The radiator came in last night, I put it in, replaced the hoses, and flushed the whole thing with distilled water one more time, Then i poured in the factory toyota red coolant... My dad told me he mixed it with distilled water at a 50/50 ratio so i trusted him and poured it in. I hadn't used the toyota stuff before so i assumed at the 50/50 ratio it was supposed to be that red. Then about 3 minute later, i found out he didnt mix it with distilled water. So i poured in the same amount of distilled water as i did coolant, of course i couldnt fit all the distilled water in, and me being the idiot that i am, i started the car to burp the system so i could get the rest in there. I didnt think to drain the coolant and remix and pour it back in...

So after fully burping the system, i thought the car was fine, i opened took it for a drive, filled up the distilled water to the top after it cooled down, topped up the overflow tank, and everything seemed fine. Then this morning i took my car to work and on the way it began to overheat. As soon as i saw it hit 3/4 of the gauge (didnt see it sooner), i turned the ac off, put the heater on full, and put the fan on max. The temp immediately dropped back to half, and i was able to make it to work. After work i topped off the rad with distilled water and sealed it back up. And drove to a friends house, he lives a decent way up a mountain, and on the way up, the car temp, climbed quickly. I pulled over, shut the engine off, popped the hood, and let it cool down. Started it up and drove up to his house. Spent a decent amount of time there. Then drove home, As i got on the freeway my temp gauge went up to 3/4 so i turned the heater on etc and the temperature went to the middle of the gauge and was steady. The only time temps would climb is when going up slight hills when the car was at 2700+rpm or on flat ground at 3000+ rpm.

Any idea what could be wrong?

Coolant has no air in the system
Don't have any apparent leaks, and the coolant doesn't drop in level any more
The coolant is a bit dirty now
Thermostat did still open after i replaced the radiator and hoses
Replaced the radiator cap with one from Napa, its rated at 13psi


Side note, When getting rid of the air in the system (car was on jacks so the front end was up in the air, Used a spill free funnel, and watched for all the air bubbles to go away like on every video i watched on youtube. I noticed The coolant rising and falling a lot more than it did in the videos. Could this be my water pump? And all the rust is the pump itself completely degraded..?

[Noahwhite2014]

Replaced the thermostat with a stant superstat rated at 180F

The old thermostat looks like crap, Super rusty, and the small washer part with the small spring could move about 1mm before it would be stuck.

After bleeding the air from the cooling system, it runs great so far. Can rev it to 6k with no change to the needle. Driving up hills at 4k rpm doesn't affect the temp at all. On the freeway i can do 3k rpm with no problems!

Hopefully this holds true tomorrow when i drive when the sun is out.